This invention relates to low melting, high solids spin finish compositions, a method for applying the compositions to fibrous substrates, and fibrous substrates treated with the high solids spin finish compositions.
Lubrication and finishing of yarns and threads, such as cotton and silk, has been practiced since ancient times. Such yarns and threads, derived from natural-occurring plants and animals such as cotton plants and silkworms, often required lubrication or finishing by xe2x80x9coilingxe2x80x9d or xe2x80x9csizingxe2x80x9d to facilitate spinning and bundling. Lubricants used were typically natural hydrophobic oils, such as mineral oil or coconut oil. Sometimes, molten waxes such as beeswax were employed which, when cooled, formed a solid lubricating finish. Usually, the fibers were xe2x80x9csizedxe2x80x9d by applying a lubricant and/or adhesive material to yarn or warp threads in a weaving operation to impart cohesion and lubricity. Historically, sizes have been hard coatings, applied neat and at a higher fiber add-on than spin finishes, and were often based on starch, wax, and other oleophilic materials. For example, U.S. Pat. No. 1,681,745 discloses a beeswax-based size for artificial silk (rayon) which is applied molten and solidifies quickly before the thread is wound up, thus assuring bundle cohesion and lubrication in all subsequent operations.
While sizes were useful in facilitating the spinning and bundling of fibers, their presence in finished articles was found to be undesirable. In particular, the oleophilic nature of the sizes was found to adversely effect the soil resistance of the finished article. Sizes also frequently compromised the appearance and handle of the article. Consequently, it became common practice to remove the size from a woven article after its manufacture by scouring the article in hot and/or detergent- containing water. In some instances, these sizes were also removed or reduced to acceptable levels as an inherent part of the dying process, as when the woven article is dyed through immersion in aqueous dye baths. However, this later methodology, in which the scouring and dying steps were effectively combined into a single process, also had its drawbacks. In particular, the presence of sizes in the dye bath frequently had adverse affects on the dying process, while also necessitating frequent replenishment of the dye solution.
After World War II, fibers were introduced which were made from synthetic polymers such as nylon, polyolefin, polyester and acrylic. These new high performance synthetic fibers required the use of special sizes called xe2x80x9cspin finishesxe2x80x9d during spinning and the subsequent fiber operations (e.g., bundling or sizing) required to produce the final woven article (e.g., fabric or carpet). The spin finish served several functions, including (1) reducing the friction developed as the synthetic fibers passed over metal and ceramic machinery surfaces, (2) imparting fiber-to-fiber lubricity, (3) minimizing electrical static charge buildup (a problem especially pronounced in the manufacture of woven articles from synthetic fibers), and, in some instances, (4) providing cohesion to the fiber. In addition, with proper use of additives, spin finish compositions could be made that were stable to high temperatures and pressures, had a controllable viscosity under application conditions, were non-corrosive, and were relatively safe to both the workers and the environment. (See Pushpa, B. et al., xe2x80x9cSpin Finishes,xe2x80x9d Colourage, Nov. 16-30, 1987 (17-26)). However, as with their sizing predecessors, the spin finishes had to be removed from the articles woven from the fibers, typically by scouring, to minimize soiling problems. See, e.g., U.S. Pat. No. 5,263,308 (Lee et al.), Col. 2, Lines 23-25.
The process of scouring, which is necessitated by the use of sizes and spin finishes, is very undesirable in that it is a tedious process which adds to manufacturing costs, while also posing water pollution problems and health concerns. See, e.g., U.S. Pat. No. 5,263,308 (Lee et al.), Col. 2, Lines 20-24. Accordingly, some attempts have been made to avoid the need for scouring by treating unscoured carpets with agents that improve the soil resistance, handle, and other characteristics of the unscoured carpet to levels acceptable for the intended end use. Thus, U.S. Pat. No. 5,756,181 (Wang et al.) and U.S. Pat. No. 5,738,687 (Kamrath et al.) describe the treatment of unscoured carpet with certain polycarboxylate salts to achieve desirable soil resistance and repellency characteristics. Similarly, U.S. Pat. No. 5,908,663 (Wang et al.) describes the topical treatment of unscoured carpets with various inorganic agents such as silica to improve the soil resistance of the carpet. However, while these treatments work quite well for their intended purpose, they require the incorporation of additional steps and materials, thereby increasing the cost and complexity of the manufacturing process. There is thus a need in the art for a method for making carpets and other woven articles that avoids the need for scouring without necessitating the use of additional treatment steps or agents.
A further problem associated with the use of many conventional spin finishes arises during the manufacturing process itself. The vast majority of spin finishes for synthetic fibers are applied from solution or dispersion in water and/or solvent. Health and safety concerns make high solvent levels in the spin finish impractical unless the solvent is non-toxic, non-flammable, and environmentally neutral. As a practical matter, this has limited the solvent selection to water. Also, aqueous dispersions of spin finishes have been preferred to neat spin finishes because the larger volume of finish applied per fiber weight results in lower application variability. Additionally, the water helps eliminate troublesome static charge, especially when formulated with other additives. (See Postman, W., xe2x80x9cSpin Finishes Explained,xe2x80x9d Textile Research Journal, July 1980 (444-453).
Several examples of aqueous spin finish compositions are known to the art. Thus, U.S. Pat. No. 5,153,046 (Murphy) describes an aqueous finish composition for imparting soil-resistant protection to textile fibers, e.g., nylon yarn, which is stable to the high shear environment of a fiber finish application system. This composition is composed of 1-35% (weight) of nonionic fluorochemical textile anti-soilant, 65-95% of nonionic water-soluble or water-emulsifiable lubricant, and 0.05-15% each of quaternary ammonium or protonated amine surfactant and nonionic surfactant. Preferred lubricants are polyethylene glycol 600 monolaurate and methoxypolyethylene glycol 400 monopelargonate.
U.S. Pat. No. 4,388,372 (Champaneria et al.) describes an improved process for making soil-resistant filaments of a synthetic linear polycarbonamide, preferably 6-nylon and 66-nylon, by applying a water-borne primary spin finish composition comprising a perfluoroalkyl ester, a modified epoxy resin and a non-ionic textile lubricant based on poly(ethylene glycol). Particularly preferred lubricants include n-butyl initiated random copolymers of ethylene/propylene oxide. At Col. 6, Lines 59-61 of the reference, it is noted that xe2x80x9cExcessive amounts of textile lubricants in the finish composition can interfere in the durability and effectiveness of the soil-resistant ingredients.xe2x80x9d Accordingly, much of the lubricant is removed at a later stage of processing when the filaments are subjected to a scouring or dyeing operation (Col. 6, lines 51-55), and application of a secondary fiber finish composition to the spun yarn is recommended at the point between the take up and windup rolls (Col. 12, lines 18-19).
U.S. Pat. No. 4,883,604 (Veitenhansl et al.) describes compositions and methods for smoothing textile fibers and sheet-form textiles made from the fibers. These compositions, which are described as solutions, emulsions, or aqueous dispersions, contain a combination of aliphatic polyether having C6-C24 alkyl radicals and containing 1 to 25 units of polymerized C2-C6 alkylene oxides and oxidized, high-density polyethylene. The concentration of aliphatic polyether in these compositions is from 5% to 30%, with the remainder of the composition being dispersants, softeners, other additives, and water. The compositions are used to improve stitching characteristics of the sheet-formed textiles, and no mention is made of improving soil-resistance or repellency.
U.S. Pat. No. 5,139,873 (Rebouillat) discloses aromatic polyamide fibers which are said to be highly processable and to have high modulus, improved surface frictional properties, scourability, deposition, fibrillation and antistatic properties. The fibers have a coating consisting of (a) 30-70% by weight of a long chain carboxylic acid ester of a long chain branched primary or secondary, saturated, monohydric alcohol, (b) 20 to 50% by weight of an emulsifying system consisting of certain nonionic surfactants, with the remainder being an antistatic agent, a corrosion inhibitor or other optional additives. The scourability of the coating is said to be very important as the residual finish level impacts the subsequent finishing in the case of fabrics (Col. 11, Lines 52-56).
However, the use of low solids aqueous dispersion spin finishes on synthetic fibers has certain disadvantages. Since water possesses a high heat of vaporization, considerable energy is required to evaporate the large quantity of water delivered to the fiber with the spin finish. Furthermore, aqueous dispersions of spin finishes can cause mechanical problems with the fiber line. For example, when conventional low solids aqueous spin finish dispersions are used, the liquid volume of spin finish required during application is fairly large, and this large volume can form non-uniform oily deposits or residues on godets, guides, winders, and other mechanical parts of the fiber-making machinery. These deposits, commonly known as xe2x80x9csling offxe2x80x9d, either drop to the factory floor or are thrown from the fiber or machinery at various points during the manufacturing process. Sling-off is highly objectionable to fiber manufacturers, due to the cost of clean-up, the damage it can cause to fiber making machinery, and the downtime associated with these problems.
Solid deposition is another major problem which can occur during production, especially when the fiber lubricant is a solid at room temperature and is applied at low solids from an aqueous dispersion. Solid deposition causes a build-up of solids on guides, rolls, and surfaces near the fiber line. The deposition problem is frequently exacerbated by the use of high viscosity spin finishes, the presence of repellent fluorochemicals in the spin finish composition, or the use of spin finish dispersions which go through a gel stage as the water evaporates from the fiber during drying. If the resulting solids are not periodically removed, they will cause fiber breaks. Unfortunately for the fiber manufacturer, the removal of solid depositions is a tedious, expensive and time-consuming process which requires a significant amount of downtime. There is thus a need in the art for spin finish compositions which provide good lubricity and other desirable spin finish characteristics, without exhibiting sling-off or solids deposition during the fiber manufacturing process.
Some attempts have been made to address the problems associated with aqueous spin finish dispersions. In particular, some neat spin finishes have been developed which are solid at room temperature but which can be applied to the fiber in a molten state at elevated temperatures.
U.S. Pat. No. 5,370,804 (Day) describes a neat lubricating finish composition comprising a natural or synthetic ester lubricant and an alkali metal salt of an aliphatic monocarboxylic acid having at least 8 carbon atoms, which melts at temperatures below 150xc2x0 C. to form a low viscosity liquid to allow uniform coating of the fibers.
U.S. Pat. No. 4,066,558 (Shay et al.) describes a neat, stable yarn lubricating composition having a viscosity of 35-65 centipoise, consisting essentially of a hydrophobic alkyl stearate lubricant, a hydrophilic alcohol ethoxylate or alkylphenol ethoxylate, an antistat and 0.1-5% of a polar coupling agent, such as water, alcohol or glycol ether.
U.S. Pat. No. 3,704,160 (Steinmiller) describes a neat secondary finish comprising oil carrier, metallic fatty acid soap, and tri-fatty acid ester which is a hard waxy material at ambient temperature but, when heated to the molten state (i.e., heated to 50-80xc2x0 C.), is suitable for treating yarn which is used downstream to make rope having desirable frictional properties for load sharing.
U.S. Pat. No. 4,900,496 (Andrews, Jr. et al.) describes a process for making tire cord made from polyamide yarn by applying a neat hydrophobic organic ester dip penetration regulator having a melting point above 27xc2x0 C.
U.S. Pat. No. 5,567,400 (Mudge et al.) describes a method for applying a low soil finish to spun synthetic textile fibers containing a dry, waxy solid component solid at room temperature comprising (a) a polyethylenimine bisamide, (b) a block copolymer or ethylene oxide and propylene oxide, (c) the reaction product of a C8-20 saturated fatty alcohol, a C8-20 saturated fatty amine, or a phenol with from 2 to 250 moles of ethylene oxide, and/or (d) a C8-22 fatty acid ester.
Japanese Published Application 6,057,541 describes a neat oil spin finish for synthetic fiber containing lubricant (e.g., butyl stearate or mineral oil), emulsifier and antistatic agent having a viscosity of less than 40 cps at 50xc2x0 C.
Japanese Published Application 7,252,727 describes a high speed spinning manufacturing process wherein polyamide multifilament is cooled to solidification and a neat oil is applied containing sorbitan ester, polyoxyalkylene polyhydric alcohol, phosphate triethanolamine and antioxidant.
Japanese Published Application 9,049,167 describes the treatment of polyurethane elastic fiber with a neat-oiling agent comprising a mineral oil/polydimethylsiloxane lubricant and an alkanolamine organic phosphate to impart antistatic properties to the fiber between spinning and winding processes and to inhibit the adherence of scum onto the machine.
German Democratic Republic Published Application 296,515 describes a spin finish for synthetic filaments comprising alkylpoly-alkyleneglycol ether lubricants with 5-15% of a liquid dicarboxylic acid diester which may be applied as a neat oil.
U.S. Pat. No. 5,263,308 (Lee et al.) describes a method for ply-twisting nylon yarns (already spun) at high speeds by coating the nylon fibers with less than about 1% by weight of a finish containing an alkyl polyoxyethylene carboxylate ester lubricant composition of the general formula R1xe2x80x94Oxe2x80x94Xnxe2x80x94(CH2)mC(O)xe2x80x94Oxe2x80x94R2, where R1 is an alkyl chain from 12 to 22 carbon atoms, X is xe2x80x94C2H4Oxe2x80x94 or a mixture of xe2x80x94C2H4Oxe2x80x94 and xe2x80x94C3H6Oxe2x80x94, n is 3 to 7, m is 1 to 3, and R2 is an alkyl chain from 1 to 3 carbon atoms. The resulting ply-twisted yarn is especially suitable for use as pile in carpets. The finish may be applied neat, although it is preferably applied from an aqueous solution or emulsion, and may be used as a primary or secondary spin finish. The reference notes that these lubricants, which are described as oils, are advantageous over other lubricants in that they may be applied at very low levels and afford ease of wash-off during dying or scouring operations, both of which lead to improved soiling repellency (see, e.g., Col. 5, Lines 10-36).
While some of the above approaches may avoid the problems of sling-off and solids deposition associated with many low solids formulations, many of these approaches also involve the use of spin finish formulations that detrimentally affect the soiling characteristics, appearance, or hand of the finished article. Consequently, the use of these formulations requires scouring, with all of the disadvantages attendant thereto. Accordingly, there remains a need in the art for a spin finish formulation that does not cause sling-off or solids deposition, while also avoiding the need for scouring of the finished article.
One possible approach to improving the soiling characteristics of articles woven from fibers containing a spin finish is to add fluorochemicals to the spin finish composition. Such spin finish compositions are known, though these compositions are typically low solids formulations. The relatively high cost of fluorochemicals relative to hydrocarbon surfactants has made it impractical to use fluorochemicals in high solids or neat spin finishes, as it would be very difficult to uniformly treat a fiber with a very low add-on level of a high solids or neat fluorochemical. Furthermore, many conventional fluorochemicals are insoluble in high solids or neat spin finish formulations.
One example of a low solids fluorochemical spin finish composition is described in U.S. Pat. No. 4,566,981 (Howells). This reference describes the treatment of fibrous substrates with mixtures or blends of (a) a mixture of cationic and non-ionic fluorochemicals, (b) a fluorochemical poly(oxyalkylene), and/or (c) a hydrocarbon nonionic surfactant, which may be a poly(oxyalkylene). The reference also teaches that the hydrocarbon surfactant has a hydrophilic/lipophilic balance (HLB) in the range of about 13 to 16, and notes that surfactants with HLB values outside of this range do not promote emulsion stability and quality. The reference indicates that the mixtures or blends disclosed therein may be applied to substrates such as carpets from a spin finish emulsion (see, e.g., Examples 44-46) to impart desirable oil and water repellency and soil resistance to the substrate. However, all of the emulsions described are low solids compositions.
Other fluorochemical fiber treatments have utilized fluorochemicals as polymer melt additives in resins to modify the surface properties of fibers extruded or spun from the resins and/or to reduce the amount of spin finish required to lubricate the fiber. Thus, U.S. Pat. No. 5,025,052 (Crater et al.) describes water- and oil-repellent fibers comprising a fiber-forming synthetic or organic polymer and a fluorochemical oxazolidinone.
U.S. Pat. No. 5,244,951 (Gardiner) describes a durably hydrophilic fiber comprising thermoplastic polymer and fluoroaliphatic group-containing non-ionic compound dispersed within said fiber and present at the surface of the fiber.
U.S. Serial No. 08/808,491 describes a plurality of filaments of a thermoplastic polymer containing a fluorochemical hydrophilicity-imparting compound, allowing for reduced levels of spin oil fiber lubricant on the fiber to impart satisfactory lubricity.
European Application 97.203812.9 describes fiber spun from filaments extruded from a mixture of a hydrophilic polymer and a hydrophilicity imparting compound, wherein the filaments have applied to them prior to spinning a spin finish comprising a fluorochemical oil and/or water repellent.
Yet another problem with conventional spin finish formulations has come to light with the emergence of polypropylene as a staple fiber in the carpet industry. Most spin finishes produced to date were developed for use on the older nylon and acrylic fibers, which have little tendency to adsorb hydrocarbon materials. In contrast to these fibers, the surface of polypropylene fibers is much more oleophilic. As a result, many conventional spin finishes are adsorbed into the polypropylene fiber surface to a much greater degree than is observed with nylon or acrylic fibers. This frequently causes degradation of the fiber, while also necessitating the use of excessive amounts of spin finish to attain desired lubricity properties.
One approach to the spin finish adsorption problem has been to add fluorochemicals to the polypropylene melt prior to the time at which the fiber is extruded, thereby rendering the fiber less oleophilic. This approach is described in some of the references noted above. However, the addition of fluorochemicals to the melt is not always desirable in that it often has an adverse effect on the hand or other characteristics of the resulting fiber.
Some spin finishes for polypropylene fibers are known outside of the carpet art, although many of these are not primary spin finishes. Thus, U.S. Pat. No. 5,246,988 (Wincklhofer et al.) describes the use of lubricants, which are the apparently liquid reaction products of 1 mole of either a C5-C36 fatty acid or alcohol with 2 to 20 moles of ethylene oxide, as carriers for hindered amine anti-oxidants. These anti-oxidants carriers are used to treat articles of high molecular weight thermoplastic films and fibers, thereby rendering the articles stable to heat and aging and allowing them to retain their breaking strength. Preferably, the lubricant comprises polyalkylene glycol (400) perlargonate, polyalkylene glycol (200) monolaurate and/or polyalkylene glycol (600) monoisostearate. However, the reference teaches that these finishes must be applied subsequent to solvent extraction of the polymer (see, e.g., Col. 4, Lines 6-10), and hence teaches the use of these materials as secondary finishes.
There is thus a need in the art for spin finish compositions which avoid the above noted infirmities associated with conventional spin finishes, and which can be used as a primary spin finish to provide good lubricity to polypropylene fibers without significant absorption into the fiber surface.
These and other needs are met by the present invention, as hereinafter described.
In one aspect, the present invention relates to a low melting, high solids spin finish composition that can be readily applied as a primary spin finish to synthetic fibers during the fiber-making process. The spin finish solids consist essentially of nonionic hydrocarbon surfactant components, such as polyoxyalkylenes, which have a  less than HLB greater than  value of from about 2 to 13.
In another aspect, the present invention relates to a method for applying the low melting, high solids spin finish composition as a primary spin finish to a synthetic fiber during the fiber-making process, thereby forming a treated fiber. In this method, the low melting, high solids spin finish composition is heated to a temperature above its melting point to form an oil. The oil is then applied to a synthetic fiber in a sufficient amount to provide lubrication to the fiber, allowing the fiber to move through the fiber-making equipment without binding of the fiber. By applying the low melting waxy solid as an oil at slightly elevated temperatures, roll build-up on the fiber machine is minimized and sometimes nearly eliminated, since the spin finish no longer undergoes the large viscosity increase upon drying which is encountered with low solids spin finish emulsions. Moreover, sling-off of spin finish from the treated fiber, a phenomenon frequently experienced with conventional spin finish compositions as the treated fiber moves rapidly through the fiber line, is drastically reduced. Soon after application, the oil re-solidifies on the fiber""s surface to form a non-oily, non-tacky fiber finish which does not detract from the performance characteristics of the article made from the fiber. In the case of carpets made from fibers treated with the spin finish compositions of the present invention, for example, the soiling characteristics of the carpet are not detrimentally affected by the presence of the spin finish, and in fact, are often improved in comparison to carpets in which any residual spin finish has been removed (e.g., by scouring). As a result, it is not necessary to remove the spin finishes of the present invention from the final article of commerce, thereby eliminating the costly and potentially polluting scouring process typically used to remove spin finishes from carpets and other such fibrous articles. Surprisingly, it is found that many waxy hydrocarbon surfactants having relatively low HLB values impart superior soil-resistant properties to the fiber and articles made from the fiber.
In yet another aspect, this invention relates to articles made from synthetic fibers treated with the low melting, high solids spin finish composition.
The present invention also relates to a low melting, high solids, water- and oil-repellent spin finish composition that can be readily applied to synthetic fibers during the fiber-making process. The solids component of this composition is a waxy material at ambient conditions having a melting point from about 25xc2x0 to 140xc2x0 C., and comprises a blend of (1) nonionic hydrocarbon surfactant component(s) having a  less than HLB greater than  value of less than about 13, and (2) compatible fluorochemical(s) having a  less than FLB greater than  value of less than 11. Such compatible fluorochemicals are found to form homogeneous solutions when blended at up to 50% by weight, preferably from about 10 to 15% by weight, with the hydrocarbon surfactant component(s) (i.e., no phase separation occurs) at typical operating temperatures. Typical operating temperatures are within the range of about 40-140xc2x0 C., preferably about 80-120xc2x0. The selection of a suitable compatible fluorochemical is not trivial, as most fluorochemicals are not compatible with hydrocarbon surfactants without the presence of external compatibilizers or without incorporating considerable amounts of solvent(s) and/or water. However, through considerable experimentation, it has been discovered that suitable compatible fluorochemicals can be selected based on a calculated quantity called fluorophilic/lipophilic balance (FLB) value. This new quantity, FLB value, is similar in concept to the HLB value for hydrocarbon surfactants, and can be calculated from the fluorochemical structure using Equation I:                               FLB          =                                                        molecular weight of the
fluorochemical segments(s)*                                            total molecular weight
 of the fluorochemical                                      xc3x97            20                          ⁢                  
                ⁢                  *includes all segments containing carbon-bonded fluorine atoms                                    EQUATION        ⁢                  xe2x80x83                ⁢        I            
To achieve compatibility between the fluorochemical(s) and hydrocarbon surfactant(s) in the absence of solvent (i.e., neat), the  less than FLB greater than  value for the fluorochemical(s) should be less than 11.
When used in spin finish compositions of this invention, some compatible fluorochemicals directly impart oil- and water-repellent properties to the fiber and articles made from the fiber. Other compatible fluorochemicals, though alone not capable of imparting significant water- and oil-repellency to the spin finish, can be used as a solubilizer to incorporate otherwise incompatible fluorochemicals (such incompatible fluorochemicals hereinafter referred to as xe2x80x9crepellent fluorochemicalsxe2x80x9d), which are known to be good water- and oil-repellents.
In another aspect, this invention relates to a method for applying the low melting, high solids, water- and oil-repellent spin finish composition to a synthetic fiber during the fiber-making process. In this method, the waxy solid is melted to form a high solids or neat oil, which is then applied to a synthetic fiber using heat traced conventional spin finish application equipment. Soon after application, the oily molten spin finish re-solidifies on the fiber""s surface to form a non-oily, non-tacky fiber finish. This finish does not impart a deleterious effect to the articles woven from the fiber (i.e., worsen carpet soiling after foot trafficking). Thus, the costly and potentially polluting scouring process, typically used to remove the spin finish from the final woven article, is eliminated. The amount of spin finish composition applied to the fiber (% SOF, or percent solids on fiber) is an amount sufficient to allow the fiber to move easily over the polished metal and ceramic parts of the fiber-making machinery without binding of the fiber.
In yet another aspect, this invention relates to articles woven from synthetic fibers treated with the low melting, high solids spin finish composition.
In yet another aspect, this invention relates to a process for making water- and oil-repellent fibers and articles woven from such fibers comprising the steps of (1) incorporating a repellent fluorochemical into a thermoplastic polymer melt, (2) extruding a fiber from the polymer melt, and (3) applying to the fiber a low melting, high solids spin finish composition consisting essentially of nonionic surfactant components having  less than HLB greater than  values of from about 2 to 13.
In yet another aspect, the present invention relates to a spin finish for polypropylene fiber. The spin finish provides the required lubricity properties without being adsorbed to a significant degree by the fiber. The spin finish also exhibits excellent antisoiling characteristics, hand, and appearance when left on the fiber in the finished article, thereby avoiding the need for scouring.
In still another aspect, the present invention relates to a method for forming a high solids, shelf-stable spin finish composition. In accordance with the method, water is added to an essentially neat polyoxyalkylene composition to form a high solids composition, with the proviso that the amount of water added is insufficient to cause the composition to turn cloudy. High solids compositions formed in this manner are found to have good shelf stability. By contrast, when the amount of water added is sufficient cause the high solids composition to turn cloudy, the resulting cloudy composition is found to exhibit poor shelf stability.
In another aspect, the present invention relates to a method for applying a spin finish composition containing a hydrocarbon surfactant and a fluorochemical emulsion to a fiber. In accordance with the method, the fluorochemical emulsion is metered or mixed into the spin finish composition and the combination quickly applied to the fiber when the fiber is ready to be spun. The method allows the blending together of a number of fluorochemical emulsions and hydrocarbon surfactants that have poor shelf stability, due, for example, to the incompatibility of these materials.
As used herein, the term xe2x80x9chigh solidsxe2x80x9d refers to a spin finish composition which contains from 70 to 100% spin finish solids and 30 to 0% solvent, the solvent typically being water. Thus, neat spin finish compositions (i.e., those containing essentially 0% solvent) are encompassed in this definition.
As used herein, the term xe2x80x9clow meltingxe2x80x9d refers to a spin finish composition whose solids are often waxy to the touch at ambient conditions and have a melting point in the range of about 25xc2x0 to 140xc2x0 C.
As used herein, the term xe2x80x9cprimary spin finishxe2x80x9d refers to a spin finish which is applied to synthetic fibers soon after they are extruded from the spinneret, cooled, and bundled, but prior to drawing.
As used herein, the term xe2x80x9cHLB valuexe2x80x9d means the hydrophilic/lipophilic balance of the surfactant. The term xe2x80x9cweighted average HLB valuexe2x80x9d ( less than HLB greater than ) means the sum of the HLB values of each separate surfactant component multiplied by that component""s percentage by weight in the spin finish composition solids.
As used herein, the term xe2x80x9cFLB valuexe2x80x9d means the fluorochemical lipophilic balance of a fluorochemical. The FLB value can be calculated from the fluorochemical structure using Equation I:                               FLB          =                                                        molecular weight of the
fluorochemical segments(s)*                                            total molecular weight
 of the fluorochemical                                      xc3x97            20                          ⁢                  
                ⁢                  *includes all segments containing carbon-bonded fluorine atoms                                    EQUATION        ⁢                  xe2x80x83                ⁢        I            
The term xe2x80x9cweighted average FLB valuexe2x80x9d ( less than FLB greater than  ) means the sum of the FLB values of each separate fluorochemical component multiplied by that component""s percentage by weight in the spin finish composition solids.
As used herein, the term xe2x80x9ccompatible fluorochemicalxe2x80x9d refers to a fluorochemical with a  less than FLB greater than  value of less than 11.
Thermoplastic polymers useful for making synthetic fibers of this invention include fiber-forming poly(alpha)olefins, polyamides, polyesters and acrylics. Preferred thermoplastic polymers are poly (alpha)olefins, including the normally solid, homo-, co- and terpolymers of aliphatic mono-1-olefins (alpha olefins) as they are generally recognized in the art. Usually, the monomers employed in making such poly(alpha)olefins contain 2 to 10 carbon atoms per molecule, although higher molecular weight monomers sometimes are used as comonomers. Blends of the polymers and copolymers prepared mechanically or in situ may also be used. Examples of monomers that can be employed in the invention include ethylene, propylene, butene-1, pentene-1, 4-methyl-pentene-1, hexene-1, and octene-1, alone, or in admixture, or in sequential polymerization systems. Examples of preferred thermoplastic poly(alpha)olefin polymers include polyethylene, polypropylene, propylene/ethylene copolymers, polybutylene and blends thereof Polypropylene is particularly preferred for use in the invention.
Processes for preparing the polymers useful in this invention are well known, and the invention is not limited to a polymer made with a particular catalyst or process.
In accordance with the present invention, a molten thermoplastic polymer fiber can be extruded through a spinneret to form a plurality of filaments (typically around 80 filaments), each filament typically having a delta-shaped cross section. The filaments are cooled, typically by passing through an air quenching apparatus maintained at or slightly below room temperature. The filaments are then bundled and directed across guides or kiss rolls, whereupon they are treated with a molten spin finish of this invention. After receiving the spin finish treatment, the filaments are generally stretched. Stretching may be accomplished over a number of godets or pull rolls that are at elevated temperatures (e.g., from 85-11 5xc2x0 C.) sufficient to soften the thermoplastic polymer. By rotating the rolls at different speeds, stretching of the filaments can be obtained. While stretching can be accomplished in one step, it may be desirable to stretch the filaments in two steps. Typically, the filaments will be stretched 3 to 4 times the extruded length (i.e., stretched at a ratio of from 3:1 to 4:1). Subsequent to stretching, and in order to obtain a carpet yarn, it is desirable to texture the yarn with pressured air at an elevated temperature (e.g., 135xc2x0 C.) or steam jet and to subject it to crimping or texturizing.
Spin finishes can be applied to fibers at different stages of the production process, depending upon what balance of performance properties are demanded from the fiber at that particular production stage. A primary spin finish is generally applied to the fibers soon after they are extruded from the spinneret, cooled, and bundled, but prior to stretching, texturizing or crimping the fiber. The primary spin finish reduces fiber-to-metal or fiber-to-ceramic friction while the fiber travels along the early stage production equipment.
Application of a secondary spin finish is often necessary during the later stage production (i.e., after stretching, crimping and texturizing of the fiber). Weaving often requires higher bundle cohesion than can be tolerated during spinning of staple fibers. The secondary spin finish imparts greater adhesion and friction to the yarn or rope made from the yarn.
While ideally the primary spin finish would have properties which eliminate the need for any secondary spin finish, this is not always possible. For example, during production, fiber-to-metal or fiber-to-ceramic friction should be low, but the final article (rope, for example) may benefit from higher friction. A primary spin finish must be optimized to allow the initial stages of yarn production to proceed in an efficient manner. If the succeeding stages have different requirements, a secondary finish will have to be applied. A secondary finish will also have to be applied if the primary spin finish is removed, or almost removed, during a processing step. For example, the majority of primary spin finish is removed during dyeing of yarn or cloth in aqueous dyeing baths. Examples of these considerations abound in the cited literature.
The low melting, high solids, optionally water- and oil-repellent spin finish composition of this invention is a waxy solid having a melting point ranging from about 25xc2x0 to about 140xc2x0 C., and more preferably from about 30xc2x0 to about 80xc2x0 C. To use a spin finish composition of this invention, the waxy solid is first melted to form an oil. Using heat traced conventional spin finish equipment, the resulting oil can be easily and uniformly applied as a spin finish to freshly made synthetic fiber at levels from about 0.2% SOF to about 4% SOF, preferably at levels from about 0.5% SOF to about 2% SOF, and more preferably at levels from about 0.75% SOF to about 1.4% SOF. The actual amount necessary for treating the fiber depends on both the spin finish composition and the oleophilicity of the fiber. For example, when a relatively oleophilic spin finish composition having a low HLB value is applied to a relatively oleophilic fiber such as polypropylene, a higher % SOF is required to provide surface lubricity to the fiber due to the absorption of the spin finish composition into the fiber.
Immediately after being applied to the fiber, the spin finish oil cools and solidifies to a lubricious solid. This lubricious solid provides sufficient lubrication to the surface of the fiber to allow the fiber to move easily past pulleys, godets, guides, winders, and other components of the fiber-making equipment. At the same time, application problems typically encountered with solid spin finish compositions, such as xe2x80x9csling offxe2x80x9d from the fiber or the deposition of spin finish solids on the machine rolls, surfaces and glides, are avoided.
In order for the low melting, high solids spin finish composition to perform effectively as a soil-resistant finish, the surfactant(s) used in the composition should have a weighted average HLB value in the range of about 2 to 13, preferably in the range of about 3 to 12. xe2x80x9cHLB valuexe2x80x9d is a term used to measure the degree of hydrophilicity of a nonionic hydrocarbon surfactant. HLB values can be calculated experimentally from the partitioning ratio of a hydrocarbon surfactant between an aliphatic hydrocarbon solvent and water. Alternatively, for hydrocarbon surfactants, HLB values can be calculated theoretically directly from their structures by summing empirically derived group numbers for each portion of the structure. For a spin finish composition containing two or more hydrocarbon surfactants, the weighted average HLB value can be calculated. For example, a formulator could achieve an HLB value of 7.5 by mixing together equal portions by weight of hydrocarbon surfactants having HLB values of 5 and 10, respectively. In general, surfactants with lower HLB values have longer hydrocarbon chains and/or a lower degree of ethoxylation, resulting in a relatively hydrophobic surfactant having low water solubility. Conversely, surfactants with higher HLB values have shorter hydrocarbon chains and/or a higher degree of ethoxylation, resulting in a relatively hydrophilic surfactant having high water solubility. (For detailed information concerning HLB values, their determinations and their measurements, see Schick, Martin J., Nonionic Surfactants, Physical Chemistry, 23, 438-456 (1987)).
The low melting, high solids spin finish compositions of the present invention are also advantageous to manufacture and use, as the expensive and troublesome emulsification step required with conventional low solids, water-based spin finishes is eliminated. Material transportation costs are also reduced due to lower volumes of neat low melting spin finish required at the production facility, and air and water pollution problems are minimized due to the absence of solvents and emulsifiers.
Preferred hydrocarbon surfactants useful in the high solids low melting spin finish compositions of this invention include polyethylene glycol 400 distearate, polyethylene glycol 300 distearate, polyethylene glycol 200 distearate, polyoxyethylene 600 distearamide and glycerol monostearate.
For a fluorochemical to be compatible with a hydrocarbon surfactant of this invention (i.e., compatible at line operating temperatures which typical are in the range of about 40-140xc2x0 C., preferably about 80-120xc2x0 C.), the fluorochemical should have an FLB value of less than 11. For example, consider the calculation of the FLB value for EtFOSE Stearate, C8F17SO2N(C2H5)C2H4OC(O)C17H35:
Molecular weight (MW) of fluorochemical segment=MW of C8F17=419
xe2x80x83Total MW=MW of C8F17SO2N(C2H5)C2H4OC(O)C17H35=837
FLB value=(419)/(837)xc3x9720=10.0
According to this calculation, EtFOSE Stearate is expected to be a compatible fluorochemical.
Now consider the calculation of the FLB value for 2MeFOSE/AZA, C8F17SO2N(CH3)CH2CH2OC(O)(CH2)7C(O)OCH2CH2N(CH3)SO2C8F17:
Molecular weight (MW) of fluorochemical segment=MW of 2xc3x97C8F17=838
Total MW=MW of 2MeFOSE/AZA=1266
FLB value=(838)/(1266)xc3x9720=13.3
According to this calculation, 2MeFOSE/AZA is not expected to be a compatible fluorochemical.
The present invention also relates to a process for making water- and oil- repellent fibers and articles woven from such fibers comprising the steps of (1) incorporating a repellent fluorochemical into a thermoplastic polymer melt, (2) extruding a fiber from the polymer melt, and (3) applying to the fiber a low melting, high solids spin finish composition consisting essentially of nonionic surfactant components having a weighted average HLB value of from about 2 to 13. Examples of suitable repellent fluorochemical polymer melt additives are well known in the art and include oxazolidinones of the type described in U.S. Pat. No. 5,025,052 (Crater et al.); esters of the type described in U.S. 5,459,188 (Sargent et al.), World Publications WO 97/22576 and WO 97/22659; U.S. Serial No. 08/901,363; imides of the type described in U.S. Pat. No. 5,681,963 (Liss); sulfones of the type described in World Publication WO 97/22660; polymerized olefins of the type described in U.S. Pat. No. 5,314,959 (Rolando et al.); piperazines of the type described in U.S. Pat. No. 5,451,622 (Boardman et al.); and amino alcohols of the type described in U.S. Pat. No. 5,380,778 (Buckanin). These repellent fluorochemical polymer melt additives can be incorporated into the fiber resin at concentrations varying from 0.1-5.0% (w/w), preferably from 0.15-1.0% (w/w), prior to spinning the fiber and applying the spin finish. Surprisingly, the fluorochemical present in the fiber can exert repellency properties through the layer of non-fluorochemical solid spin finish present on the surface of the fiber.